The miniSLR: A low-cost, high-performance laser ranging system for the ILRS

The miniSLR® has been developed as a low-cost, high-performance alternative to conventional SLR systems. It is completely integrated into a movable container of less than 2 x 2 m² footprint. Using a 500 ps laser at 50 kHz repetition rate, it achieves sub-centimetre precision. Long-term stability has been considered as integral part of the design and is facilitated by a full encapsulation, air-conditioning, short cable lengths and a calibration target on the main support structure. While the focus is on LEO targets including Lageos, all targets including GNSS constellations can be ranged. The main advantages of such a small, highly integrated system are rather obvious: Low production cost, reduced engineering effort, shorter commissioning times. The system can be constructed and validated at the factory, before it is transported to its final observation site. At the site, no civil works are required and no building permits need to be obtained. Yet the system can be connected firmly to the ground, and using an appropriate site survey, local ties can be established in the same way as for conventional systems. At DLR in Stuttgart, tests with an improved miniSLR® prototype have commenced in March 2022. Minor modifications for improved stability and reliability are underway. In July 2022, the system has been accepted into the ILRS as engineering station. It is planned to regularly deliver data to the ILRS to validate the system performance and stability. Furthermore, DLR will use the system as a test platform for its own research, including experiments with smart retroreflectors which can be used for satellite identification

Compact setup for standoff Laser induced breakdown spectroscopy of radioactive materials

Radioactive materials present a major threat and can cause severe direct and long term injuries to humans as experienced i.e. in the Fukushima and Chernobyl nuclear plant catastrophes. Furthermore, intended use of radiological dispersal devices can be used to spread radioactive materials over large areas. Detecting these hazards and investigating the status of contaminated areas a remote standoff determination of nuclear fission products would serve as a helpful tool for first responders and damage control teams. Laser induced breakdown spectroscopy (LIBS) offers a unique possibility for the identification of elements as nuclear fission products and is even able to distinguish different isotopes of the same species. Within this scope and based on experiences with a high power / long distance (> 100 m) LIBS setup we present a new compact and low power setup. The compactness allows for handheld operation as well as mounted on a small robot or on an unmanned aerial vehicle (UAV) an advanced setup could be controlled remotely and would be able to safely determine radioactive materials

Position determination of resident space objects via triangulation with two passive-optical staring systems

The number of space objects orbiting the Earth is rapidly increasing. An opportunity to detect and measure the position of space objects are passive optical staring systems, e.g. our system called APPARILLO. While staring systems are capable of measuring highly accurate equatorial coordinates of space objects via an astrometric calibration, they do not provide information on their altitude unless the space object is assumed to fly on a circular orbit. In this work we discuss an approach in which the altitude of a space object is measured via triangulation (simultaneous observation with two staring systems placed at different positions on Earth). Based on theoretical calculations, we estimate that the triangulation with two staring systems can provide the altitude of a typical space object in a low Earth orbit with an accuracy as low as 200 m. This is two orders of magnitude better compared to a simple circular orbit approximation that can be used for a single staring system

Lasertechnik für das Verkehrsmanagement im All: Technologien für eine nachhaltige Raumfahrt

Die stark zunehmende Anzahl an Satelliten ermöglicht großen Fortschritt in der Wissenschaft und Technik und eröffnet neue Möglichkeiten wie ein weltweit verfügbares Internet. Gleichzeitig sind damit Herausforderungen für das Verkehrsmanagement im Weltraum (meist Englisch als Space Traffic Management bezeichnet) verbunden. Simulationen zeigen, dass die Anzahl an Kollisionswarnungen im niedrigen Erdorbit allein durch den Ausbau von 5 Megakonstellationen (Starlink, OneWeb, Amazon Kuiper, Guo Wang und SatRevolution) mit insgesamt ca. 70000 Satelliten etwa um den Faktor 4000 ansteigen wird. Durch weitere Satelliten und zusätzlichen Weltraummüll wird diese Zunahme real weitaus größer sein. Selbst wenn sich Kollisionen durch Ausweichmanöver verhindern lassen, verursachen diese hohe Kosten. Um die Anzahl an notwendigen Ausweichmanövern zu reduzieren und die weiterhin notwendigen Manöver effizient zu machen, ist eine hochpräzise Vermessung der Bahndaten der Weltraumobjekte erforderlich. Je genauer die Bahndaten sind, desto kleiner ist der Abstand in dem die Weltraumobjekte bei gleichem Kollisionsrisiko aneinander vorbeifliegen können. Beim Satellitenlaserranging (SLR) wird die Laufzeit eines gepulsten Lasers vermessen, der von einer Bodenstation emittiert und durch einen am Satelliten befestigten Retroreflektor wieder antiparallel zu dieser zurück reflektiert wird. Dadurch lassen sich millimetergenaue Abstände ermitteln, aus denen die Bahndaten des Satelliten errechnet werden. Da diese Messungen viel präzisiere Daten liefern als derzeit verfügbar, würden ca. 99% aller Ausweichmanöver unnötig werden. In Zusammenarbeit mit der Industrie entwickeln wir eine kompakte und transportable SLR Bodenstation, das miniSLR®. Hiermit konnte kürzlich gezeigt werden, dass trotz der kompakten, kostengünstigen Bauweise und der Nutzung von, gegenüber anderen SLR Stationen, verhältnismäßig langen Laserpulse durch Datenmittelung Millimeter präzise Abstandsmessungen erzielt werden. Um den Nutzen der SLR Technologie für das Space Traffic Management weiter zu erhöhen, arbeiten wir weiterhin an der Entwicklung von polarimetrischem SLR. Dies soll neben der Bahnvermessung auch eine Identifikation von Satelliten (z.B. nach Massenstarts von Kleinsatelliten) ermöglichen. Hierfür werden spezielle Retroreflektoren entwickelt, welche für die Raumfahrt qualifiziert und in zukünftigen Missionen getestet werden sollen

The miniSLR: a low-budget, high-performance satellite laser ranging ground station

Satellite Laser Ranging (SLR) is an established technique providing very accurate position measurements of satellites in Earth orbit. However, despite decades of development, it remains a complex and expensive technology, which impedes its further growth to new applications and users. The miniSLR implements a complete SLR system within a small, transportable enclosure. Through this design, costs of ownership can be reduced significantly, and the process of establishing a new SLR site is greatly simplified. A number of novel technical solutions have been implemented to achieve a good laser ranging performance despite the small size and simplified design. Data from the initial six months of test operation have been used to generate a first estimation of the system performance. The data include measurements to many of the important SLR satellites, such as Lageos, Etalon and most of the geodetic and Earth observation missions in LEO. It is shown that the miniSLR achieves sub-centimetre accuracy, comparable with conventional SLR systems. The miniSLR is an engineering station in the International Laser Ranging Service and supplies data to the community. Continuous efforts are undertaken to further improve the system operation and stability

Polarimetric satellite laser ranging

We report on concepts and laboratory experiments pioneering polarization-modulated SLR. The idea is to equip satellites with specially designed retroreflectors with different polarizing properties. These retroreflectors can be coded into arrays and act as an identifier for satellites (a number plate) that can be read from ground), while maintaining the precise orbit determining capability of conventional SLR. The intended demonstration of the technology in a space mission not only requires the design of new retroflectors with additional polarization op-tics, but also modifications to our SLR station (the miniSLR) in terms of hardware and software to be able to emit and detect photons with different states of polarization